Flying electric generators with clean air rotors

ABSTRACT

Flying electric generator aircraft that include groupings of four rotors mounted to booms extending fore and aft of a fuselage structure wherein the rotors are placed so that when the aircraft is facing the wind, each rotor has a direct path to an undisturbed flow of air, regardless of pitch angle and during all flight maneuvers of the aircraft. The rotors are placed in counter-rotating pairs with the booms preferably angled so that the rotors in the front of the aircraft are spaced at a distance from one another that is different than a spacing of the rotors at the rear of the aircraft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to the field of flying electricalgenerators (FEGs) and, more particularly, to new configurations ofFlying Electric Generators (FEGs) featuring rotors positioned on a frameor body such that each rotor receives clean air which is undisturbed bythe other rotors mounted to the frame or body.

2. Brief Description of the Related Art

Flying Electric Generators are not new and several methods of extractingenergy from high altitude winds have been proposed and are now indevelopment. It is well known that the energy content in wind increaseswith distance from the ground (altitude). Current ground based windturbine technologies attempt to take advantage of this fact by mountingwind driven rotors at greater heights and by extending blades to greaterlengths. However, due to the cantilever design of ground based winddriven generators, there is a limit to their maximum height, as largeand costly steel and concrete bases are required to counter the bendingforces introduced by their necessary structural geometry. FEGs, incontrast, need only a thin, light tether attached to a small groundanchor point to counter or react to the force of the wind, and they canfly high above the ground and into the most concentrated and abundantnatural energy source, the high altitude winds.

Currently, and as shown in FIGS. 1 and 2, autogyro rotor based FEGs, 10,10′, respectively, in development have at least four rotors, with tworotors 11, 11′ and 13, 13′ rotating in one direction, and two rotors 12,12′ and 14, 14′ rotating in the other direction. The most commonly seenconfiguration includes four rotors mounted in a symmetric square patternto an X-shaped frame or fuselage 15, as shown in FIG. 1, or to anH-shaped frame or fuselage, as shown in FIG. 2. Other symmetricconfigurations have been studied, including those with larger numbers ofrotors with even numbers of sets of counter rotating pairs of rotors.For example, as shown in FIG. 3, an eight rotor FEG could have fourrotors 16A-16D clustered in a square pattern, with four more rotors17A-17D in another square pattern positioned 45 degrees to the rotors16A-16D. As shown, the rotors which are diagonally positioned relativeto one another in each square have blades rotating in one directionwhich is opposite that of the two other diagonally positioned rotors ineach square. This configuration would be suitable for a hoveringplatform multi-rotor helicopter, but symmetrically spaced rotors createproblems for FEG applications.

During flight of prior art FEGs, when an angle of attack of the rotorsis at a relatively small angle, see the discussion below with respect tothe angle of attack with respect to the FEGs of the present inventionand shown in FIGS. 4 and 5, the downward component of the air flowemerging downwind of each forward rotor causes a reduction in thrust ofan aft rotor directly downwind. This is because the downward componentof flow behind the forward rotor changes the apparent wind direction forthe aft rotor. The apparent wind experienced by an aft rotor downwind ofa forward rotor has a downward component, which is equivalent to arelative reduction in pitch angle for that aft rotor. Reduction of pitchangle reduces thrust. The result of the loss of thrust in an aft rotoris a rapid and uncontrolled increase in vehicle pitch. During testing,this interaction was discovered and the present invention has been madeto eliminate this problem.

The foregoing problem disappears when an angle of attack becomes large,but the problem area, flight in wind with taught tether at low positivepitch angles, must be traversed to achieve the larger angle of attack.At large positive angles of attack, the forward rotors are so far abovethe aft and downwind rotors that the downward-directed flow trailing theforward rotor does not always reach the aft rotor, and it operates insomewhat undisturbed air.

SUMMARY OF THE INVENTION

This invention is directed to configurations of rotor placements forFEGs that allow four rotors to operate in clean, undisturbed air duringall flight maneuvers. The rotors are placed so that when the FEG isfacing the wind, each rotor has a direct path to an undisturbed flow ofwind, regardless of pitch angle. The rotors are placed incounter-rotating pairs so that the FEG is controlled in the same way asall previous FEG designs with tightly clustered rotors.

Advantages of the invention over related art include that an FEG can becontrolled by means of varying thrust of rotors alone during allportions of flight from takeoff through power generation and landing.Because each rotor receives undisturbed direct wind energy at all phasesof flight, there are no discontinuities in control based on angle ofattack and wind speed. This allows for a smooth transition from takeoffand hovering flight to kite-like power generating flight. Previous FEGdesigns with closely clustered rotor placements would either need to belaunched with a high angle of attack with a tight tether, or make anabrupt, partially controlled fast pitch maneuver from low angles ofpitch to high angles of pitch where the closely spaced rotors will nolonger cause loss of thrust in the downwind or aft rotors.

In accordance with the invention, a fuselage is configured having acentral housing preferably fabricated from a combination of machinedaluminum plates and formed sheets, but also could be fabricated from amulti-part or monolithic composite material. The central housing housesthe avionics and computer systems necessary for FEG control, theelectronics necessary to communicate with the ground, motor controlelectronics, and power conversion electronics. The housing includes aframe structure having upper and lower ring-like components. Four rotorsupport arms or booms, preferably formed as hollow tubes, are connectedto the upper and lower ring-like components with two of the armsextending forward of the central housing and supporting forward rotorsand two of the arms extending aft of the housing and support two aftrotors. The rotors are carried by rotor mounting assemblies secured tofree ends of the arms.

The forward rotors are spaced closely to one another such that tips ofthe rotor blades pass close to one another as they rotate. The aftrotors are spaced farther apart relative to one another and they are notaffected by air passing through the forward rotors such that only cleanair, undisturbed wind, enters the blades of the aft rotors duringflight. Preferably, the forward rotors are spaced apart at an angle ofat least approximately 90° relative to one another and the angle may begreater, however, in the preferred embodiments, the aft rotors will bespaced apart at a greater angle than the forward rotors. Also, inpreferred embodiments, the forward arms are shorter than the aft armssuch that the forward rotors are more closely spaced relative to oneanother than the aft rotors.

An electric motor such as a permanent magnet DC servo motor is carriedby each of the rotor mounting assemblies with each motor beingmechanically connected to the rotor blades and electrically connected toseparate electronic motor controllers mounted to the central housing.The motor controllers function as switching devices for permittingcurrent flow to the motors from a ground power source connected theretoby electrical conductors which extend through the tether by way of whichthe FEG is connected to a ground anchor during flight. The current flowto the motors provides power to rotate the rotor blades during ascentand descent, and at some other times, during a flight of the FEG.However, during power generation flight in a kite-like mode of the FEG,the voltage generated by a regenerative braking of the motor drive shaftdue to the power of the wind against the blades, the motor controllerswitches to allow current to flow from the motor to a ground level powergrid, power storage device or some other device to be electricallypowered by the FEG.

Also mounted to each rotor mounting assembly is a pitch control servowhich controls the pitch angle of the rotor blades. The pitch controlservo alters a position of a servo wheel or horn which is mechanicallylinked to a pitch control ring which is non-rotationally mounted about avertically adjustable sleeve that is mounted to rotate with a bladesupport knuckle assembly. A pair of oppositely oriented blade grips,from which the blades of the rotor extend, are adjustable mounted to theknuckle assemble about an axis substantially perpendicular to therotational axis of the rotor blades so as to change the pitch of therotor blades depending upon the operation of the pitch control servo.Each blade grip includes a lever having a pitch horn which ismechanically connected to the pitch control ring such that as the ringis raised and lowered relative to the rotor knuckle assembly by theaction of the pitch control servo, the pitch angle of the blades ischanged.

The central housing of the fuselage also houses electrical connectorsfor connecting the electrical conductors in the FEG tether as well as acentrally mounted yoke for securing the tether to the frame of thehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had withreference to the accompanying drawings wherein:

FIG. 1 is top plan illustrational view of a conventional prior art FEGhaving one configuration of placement where the rotors are mounted in agenerally X-shaped configuration;

FIG. 2 is a top plan similar to FIG. 1 but showing the rotors placed inan H-shaped configuration;

FIG. 3 is a top plan view of FEG having eight rotors mounted in two boxshaped configurations with the outer box being offset approximately 45degrees relative to the inner box;

FIG. 4 is a side illustrational view of the FEG of the present inventionshown in FIG. 7 having portions broken away with the FEG tethered to theground with the angle of wind flow being shown downwardly from a frontor fore rotor relative to a rear or aft rotor and showing the pitchangle of attack “Δ” of the FEG relative to a wind direction “W”;

FIG. 5 is a side illustration view of the FEG of FIG. 4 showing an angleof attack with a reduced pitch angle;

FIG. 6 is a bottom plan illustrational view of the FEG in accordancewith the teachings of the present invention;

FIG. 7 is a bottom perspective view of a first embodiment of FEG of thepresent invention showing four rotors, four fuselage boom arms extendingfrom a central control housing of the fuselage and drive motors for therotors;

FIG. 8 is a perspective view of the central housing area of the fuselageof the FEG of FIG. 7 having portions broken away to show the mounting ofone of the rotor support boom arms of the fuselage;

FIG. 9 is a bottom perspective view of the central housing of FIG. 8showing the connection of the rotor support boom arms and a tetherattachment in greater detail;

FIG. 10 is a side perspective view of one of the rotor mountingassemblies of the invention showing a motor for driving the rotor bladesand for developing power for generation back to ground and also showingthe mechanical pitch control devices for altering the pitch of the rotorblades;

FIG. 11 is a bottom perspective view having portions broken away showingthe rotor mounting assembly of FIG. 10 and the drive connection betweenthe motor for the rotor blades and the rotor drive shaft;

FIG. 12 is a top illustrational view of another embodiment of FEG inaccordance with the teachings of the present invention wherein eightrotors are mounted on a fuselage in such spaced relationships that thefore or front rotors do not interfere with the clean wind flow to therear or aft rotors; and

FIG. 13 is a bottom perspective view of the FEG of FIG. 12 showing atethering arrangement for power conductor tethers between the FEG andthe ground.

FIG. 14 is a bottom perspective view of the FEG of FIG. 12 showing analternative tethering arrangement for power conductor tethers betweenthe FEG and the ground.

FIG. 15 is a side illustrational view of the FEG of FIG. 12 showing atethering arrangement option.

FIG. 16 is a side illustrational view of the FEG of FIG. 12 showing therotation of the fuselage forward arms or fuselage aft arms or boomsabout the fuselage.

FIG. 17 is a top illustrational view of another embodiment of FEG inaccordance with the teachings of the present invention wherein four ormore rotors are connected longitudinally on a front to four or morerotors on an aft fuselage, the front and aft fuselages connectedtransversely by two or more booms.

FIG. 18 is a side illustrational view of the FEG of FIG. 17.

FIG. 19 is a bottom perspective view of the FEG of FIG. 17 showing anoptional tethering arrangement for power connector tethers between theFEG and the ground.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With continued reference to FIGS. 4-13 of the drawings, the invention isdirected an arrangement of rotors for an autogyro Flying ElectricGenerator (hereinafter FEG) 20 where all rotors are able to receivedirect, undisturbed wind when the FEG is pointed or directed into thewind regardless of pitch angle. As shown in FIG. 6, in order for the FEGto be controlled by varying rotor thrusts as described herein, therotors must be installed in sets of counter-rotating pairs, with atleast four rotors. The rotors must be placed so that the center ofgravity (CG) is at the geometric center of the rotor areas, and so thatthere is an equal distance from a rotor on the left of the CG to itscounter-rotating counterpart on the right of the CG, also the distanceof a rotor behind the CG must be equal to the distance of itscounterpart ahead of the CG.

The simplest embodiment of this design is a FEG with four rotors, thefront (upwind) pair of rotors 22 and 23 are mounted to forward extendingrotor support arms or booms 24A and 24B of a fuselage 25 having acentral housing 26 to which the arms 24A and 24B are mounted. Thefuselage also has two rearwardly extending or aft arms or booms 27A and27B to which a pair of aft or downwind rotors 28 and 29 are mounted. Theforward rotors 22 and 23 are set near each other, as shown in FIG. 7, sothat only a small distance separates the blade tips as they rotate. Theaft rotors are spaced farther apart relative to one another so that theyare not effected by air passing through the forward rotors such thatonly clean air, undisturbed wind, enters the blades of the aft rotorsduring flight. Preferably, the forward rotors are spaced apart at anangle of up to at least approximately 90° relative to one another, andthe angle may be greater, however, in the preferred embodiments, the aftrotors will be spaced apart at a greater angle than the forward rotors.Also, in some embodiments, such as shown in FIG. 7, the forward arms areshorter than the aft arms such that the forward rotors are more closelyspaced relative to one another than the aft rotors.

The forward rotors must rotate in opposite directions as shown by thearrows in FIG. 6, but the clockwise rotor may be either on the right orleft. The aft (downwind) rotors 28 and 29 are spaced much farther apartand far enough apart such that a line L1 extending from the righttangent edge of a circle C1 swept out by the right forward rotor tip 23does not intersect a circle C2 swept out by the right aft rotor tip 29.In a like manner, the rear left rotor tip must be spaced outwardlyrelative to a tangent line L2 extending from a left tangent edge of acircle C3 swept by the forward rotor tip 22 so that the line L2 does notintersect a circle C4 swept by the left aft rotor 28. The right and leftrotors of the aft pair must also rotate in opposite directions, and eachmust rotate in the opposite direction from the front rotor nearest toit. This also means that each aft rotor is rotating in the samedirection as the forward rotor on the opposite side of the FEG 20 fromit.

As shown in FIG. 7, the fuselage 25 includes a central housing 26 towhich a tether 31 is secured and which extends to a ground station “S”,see FIGS. 4 and 5. The tether 31 includes both an electrical cable and areinforced anchor cable that is designed to permit deployment of the FEG20 to high altitudes to facilitate power generation.

With reference to FIGS. 8 and 9, details of the central housing of thefuselage are shown in detail. As previously described, the housing ispreferably fabricated from a combination of machined aluminum plates andformed sheets, but also could be fabricated from a multi-part ormonolithic composite material. The center housing contains the avionicsand computer systems necessary for FEG control, the electronicsnecessary to communicate with the ground, motor control electronics, andpower conversion electronics. The housing includes a frame 32 havingupper and lower ring members 33 and 34 of the same general shape. Asshown, the rings have four equally sized straight sides 35 which areconnected by diagonally extending corner members 36 each have two pairof spaced mounting lugs 38 extending outwardly from opposite endsthereof. The pairs of lugs have aligned openings therein for receivinglocking pins 40. The locking pins include spring loading locking balls41, which, after the pins are in place, extend outwardly of the pins toprevent withdrawal of the locking pins from the lugs 38 unless the ballsare depressed within the pins.

The upper and lower frame rings are connected by generally U-shapedcorner panels 42 which are retained in position by the lugs 38 andlocking pins 40. The corner panels 42 including openings 43 and 44 forpassage of electrical wire harnesses (not shown) to motors 45 and arotor pitch control servo 46 which are mounted on rotor supportassemblies 48 mounted at the ends of each of the two forward and two aftextending rotor support boom arms, as shown in FIG. 10.

To mount the four rotor support arms 24A, 24B, 27A and 27B to thecentral housing 26 of fuselage 25, their inner ends are positionedbetween pairs of reinforcing triangularly shaped panels 50. In thepreferred embodiment, each arm is constructed as a hollow tubular boomstructure formed of preferably round sectioned thin wall carbon fiberreinforced epoxy construction, though oval or other shape cross sectionsand other materials such as Kevlar or fiberglass composites or highstrength aluminum alloys such as 6061 may also be used. Streamlined orairfoil cross-sectional tubing or composite structures may be used forthe arms, and these may be oriented to give additional lift at certainpitch angles, especially when the FEG vehicle is in kite-like flight. Tosecure the arms to the central housing 26, a pair of aluminum lugs orcollars 52 are bonded about the inner end of each arm and spacedapproximately a foot from the inner end as shown in FIG. 8. The collarshave flat outer edges with tapped holes for receiving screws used tosecure the pair of panels 50 along the opposite sides of the arm. InFIG. 8, the right side panel 50 has been removed so as to show aninverted U-shaped reinforcing panel 51 which extends from the upperframe ring 33 diagonally outwardly and downwardly to a point ofattachment with the collar 52. In this manner, the panels 50 and 51provide for the cantilevered support for each arm of the fuselage.

With continued reference to FIG. 8, the FEG includes four motorcontrollers mounted within housings 54 with each controller beingelectrically connected to a rotor motor 45 and the rotor pitch controlservos mounted on the same arm. The motor controller housings aremounted to the reinforcing panels 51, with one controller being removedto show the underlying panel 51 in FIG. 8. The controller housingsprotect the controllers from adverse ambient conditions during the useof the FEG.

Also shown in FIG. 9 is a tether connecting yoke 55 which is pivotallymounted to pin 56 carried by a reinforced beam element 58 mounted so asto be supported by the frame of the central housing. The yoke ispreferably positioned at the center of gravity of the FEG.

With reference to FIGS. 10 and 11, the details of the rotor structuresand controls will be described in detail. The motor 45 associated witheach rotor is preferably a DC servo motor having inner permanent magnetswhich rotate within a series of coils. Power to and from the coils iscontrolled by the motor controllers. The motor controllers function asswitching devices for permitting current flow to the motors from aground power source connected thereto by electrical conductors whichextend through the tether by way of which the FEG is connected to theground anchor during flight. The current flow to the motors providespower to rotate the rotor blades 60 during ascent and descent, and atsome other times, during a flight of the FEG. However, during powergeneration flight in a kite-like mode of the FEG, the voltage generatedby a regenerative braking of the motor drive shaft due to the power ofthe wind against the blades 60, the motor controller switches to allowcurrent to flow from the motor 45 to a ground level power grid, powerstorage device such as a battery or some other device to be electricallypowered by the FEG. By way of example only, supposing power from theground source has a maximum voltage of 400 volts. As wind places a loadagainst the rotor blades there is a reverse load or torque placed on themotor drive shaft which increases the voltage being produced by aregenerative braking effect on the motor. When the reverse voltageexceeds 400 volts, the voltage controller switches current flow from theFEG to the collector grid or device at the ground or to some device tobe powered from the FEG. When the power developed by the wind againstthe blades drops to a predetermined level, the controller switchescurrent flow from the ground source back to the motor.

Each motor 45 is mounted to a rotor support assembly 48 which is fixedlysecured to the outer end of a related fuselage boom arm. The outer endof the boom arm is reinforced by a connector 57 that is mountedpartially within the outer portion of the arm. The connector is mountedbetween two opposing metal plates 58 which are connected by a pluralityof spacer members 59. The plates are notched and a motor supportplatform 61 is secured to the notched portion of the plates. In someembodiments, the outer ends of the arms may include one or more collarssimilar to those described above for securing the inner portion of thearms to the central housing, which collars would be secured to the rotorsupport assembly.

Each rotor motor 45 has an output shaft 62 connected to a gear 63 thatmeshes with a larger gear 64 fixedly mounted to a rotor drive shaft 65.The lower end of the drive shaft 65 is mounted within a lower bearing 66carried by a lower frame of the rotor support assembly 48. The driveshaft 65 also extends through a similar upper bearing 68 mounted to therotor support assembly 48. The upper end of the drive shaft 65 isfixedly mounted to a rotor blade knuckle assembly 70 that rotates withthe drive shaft and to which are mounted a pair of oppositely orientedbifurcated blade grip members 72 to which root portions 73 of the rotorblades are secured. Fixedly connected to each grip member is a lever 74carrying a pitch horn 75 that is connected to an upper connector 76 ofan adjustable ball joint linkage 77. The linkage 77 also includes acentral threaded section 78 and a lower connector 79 that is connectedto a vertically movable sleeve 80. The sleeve 80 is slidably movablealong a pair of guide pins 82 that are secured and depend from theknuckle assembly 70. The sleeve 80, ball joint adjustment link 77, pitchhorn 75, lever 74 and blade grip member 72 form a portion of a bladepitch adjustment assembly that is controlled by an on board computer 112in response to flying conditions including wind speeds and directions,altitudes, torque conditions on the rotor motor and desired flyingconditions such as whether the FEG is ascending or descending. It shouldbe noted that both blade grips are connected to the movable sleeve 80such that the pitch of each rotor blade is simultaneously adjusted.

The blade pitch adjustment assembly further includes a pitch controlring 84 that is fixedly mounted about the rotatable sleeve 80. A heavyduty bearing 85 is mounted to the ring and the sleeve 80 is rotatablymounted to the bearing such that as the ring is moved verticallyrelative to the blade drive shaft 65, the sleeve will be moved with thering. As the sleeve moves up and down as it rotates with the blades, theball joint linkage 77 will urge the lever 74 to rotate the blade gripconnected thereto about an axis B-B that extends perpendicularlyrelative an axis of rotation A-A of the blade drive shaft to therebychange the pitch angle of the rotor blade. As shown, the pitch controlring 84 includes a guide pin 87 that extends between a pair of closelyspaced vertically oriented guide pins 88 which prevent the ring frommoving side to side relative to the blade drive shaft as the ring israised and lowered relative thereto.

Control of the pitch control ring 84 is initiated by a pitch controlservo motor 46 mounted to one of the side plates 58 of the rotor supportassembly. The motor 46 drives a drive wheel 92 which is connected to aservo horn 93 extending from an end connector 94 of an adjustable balljoint linkage 95. The linkage 95 has a central threaded section and aspaced connector 96 pivotally mounted to a crank arm 97 which is fixedto a pivot shaft 98 that extends between the two side plates 58 of therotor support assembly. The opposite end of the pivot shaft 98 is fixedto a lever, not shown, so that the lever on the opposite side of theblade support assembly will move concurrently with the upper end 99 ofthe crank arm 97 in order to control adjustable ball joint linkages 100,provided on opposite sides of the blade support assembly. The linkages100 each include lower connectors pivotally connected at 101 to theupper end 99 of the crank arm and an opposite lever, not shown. Thelinkages 100 also include central threaded portions 103 and upperconnectors 104 that are pivotally engaged with pivot members 105 mountedon opposite sides of the pitch control ring.

In operation of the pitch control assembly, in response to the servomotor 90, the linkage 95, located on only one side of the rotor supportassembly, will move the crank arm 97 and the oppositely located leverwith the pivot shaft 98 to either raise or lower the linkages 100 toraise or lower the pitch control ring and thereby cause a pitchadjustment to the rotor blade as previously described.

As previously noted, the spacing of the rotors of the FEG 20, as shownin FIGS. 6 and 7, is such that, in the direction of the wind shown byarrow “W”, none of the back drafts from the front rotors adverselyeffects clean air entering the aft rotors.

The central housing structure 26 may also contain a reaction point forthe tether, if the tether is a single point attachment. The single pointtether must be attached at a point that is both the FEG center ofgravity and the geometric center of the rotor swept areas. As thetension in the tether changes due to varying wind speeds, tether forcescan disturb the vehicle stability if it is not attached at this point bygenerating moments that would induce rotation of the vehicle. The singlepoint tether is preferred for smaller FEGs 20.

During use, the FEG 20 flies up from the ground and hovers as amulti-rotor helicopter, and for this part of the flight, the tightlyclustered symmetric arrangement of rotors is preferred. For takeoff andhovering, the FEG consumes electric power which is provided from a powergrid or a generator at ground level, depending on the application.Electric power from the ground is transmitted through conductors in thetether 31 and is used to create torque in the drive motors for each ofthe rotors. The drive motors and their controllers are designed toconvert electric power coming up the tether from the ground into torqueto turn the rotors, and also to convert excess torque available at therotors into electrical energy to send down the same conductors in thetether for use on the ground. Rotors generate thrust by moving airdownward, through the rotor blades. The amount of thrust is controlledeither by rotational speed of the rotors, using a fixed pitch blade, orby varying the pitch of the blades while they are rotating at a constantrotational speed, or by a combination of the two techniques.

As the rotors create thrust, they require torque input to rotate. Theamount of torque required times the rotational rate of the rotor is thepower required to maintain that level of thrust. The torque input tokeep the rotor turning and create thrust also results in a reactiontorque from the air against the rotor. This torque is proportional tothe thrust, and because there are pairs of rotors rotating in oppositedirections, this torque is normally balanced if each rotor is producingthe same thrust.

It is possible to control the FEG 20 rotation about a vertical axis,called yaw, by reducing the thrust of one pair of rotors rotating in onedirection while increasing the thrust of another pair of rotors rotatingin the opposite direction. If this is done to maintain the total thrustlevel constant, the FEG will only rotate in yaw, and maintainorientation about the pitch and roll axes, and its position. For the FEGto roll change orientation about the roll (longitudinal) axis or pitch(transverse) axis, the thrust is increased on the side of the FEGdesired to rise, and decreased on the side desired to lower. Maneuverscan be combined as required, with roll, pitch and yaw rotations donesimultaneously.

For the FEG 20 to climb, overall thrust is increased and the FEGaccelerates upward, descending is the opposite. For the FEG to movelaterally, it is rolled or pitched so that a portion of the overallthrust vector is inclined in the direction desired, this component ofthrust will accelerate the FEG in that direction. Once the FEG 20 hasaccelerated to the desired travel speed in a direction, it is leveledout to maintain that speed. The FEG 20 is stopped by rolling and orpitching in the opposite direction to the velocity until the FEG hasdecelerated to zero speed.

Once the FEG 20 climbs to a predetermined altitude for generation ofpower using high velocity winds, it flies downwind to a position wherethe tether angle with the ground is acceptable for the wind conditionsand space available. The horizontal component of the tension in thetether now reacts with the force of the wind on the FEG 20. Thepreferred configuration of the FEG 20 has a wider fuselage and rotorspacing at the aft than it does at the front, and will naturally rotatein yaw like a weather vane to face into the wind. This is caused by anunbalance in drag from the unequally spaced rotors on each side of thetether. As the vehicle yaws to face the wind, the drag on each sidebalances and the vehicle will maintain a heading. Next, the FEG 20 iscommanded to gradually pitch up to a large angle of attack e, see FIG.4. The positive pitch angle of attack exposes the underside of therotors to the wind. The thrust of the rotors now has a down-windcomponent, plus a vertical component. The vertical component of thrustmust remain equal to the FEG 20 weight plus the vertical component oftether tension where it attaches to the FEG 20 or the FEG 20 will climbor descend. Because the rotor area now exposed to the wind hasincreased, the thrust also increases. The larger the pitch angle, thelarger the exposed area and the larger the thrust. As the FEG 20 angleof attack is increasing, the blade pitch of the rotors must be decreasedto limit thrust increase, so that the vertical component of thrust doesnot increase. The inflow of the wind under the rotors applies a torqueto the rotors, which drives them to a faster rotational rate, and thisaccelerating torque increases with reduced rotor blade pitch.

To prevent the rotors from accelerating to a faster rotational rate, theelectric motors apply torque in the direction against this acceleration,which creates electric power that is sent down the conductors in thetether for use on the ground. This reverse torque due to the force ofwind on the rotor blades is referred to as a regenerative brakingprocess for the motors wherein the voltage being created by the brakingprocess overcomes the voltage of the current being supplied from theground through the tether. When this occurs, current flow is from theFEG 20 to the ground. The flow of current for each motor is controlledthrough the motor controllers which act like switches and whichcontinuously monitor operative conditions within each permanent magnetDC motor of the FEG. When the pitch maneuver is complete, the FEG isflying like a kite, with a large pitch angle of attack, and the tethertension balancing the force of the wind on the FEG.

The transition from hovering flight to flying like a kite is done over aperiod of less than a minute. This is a simple increase in pitch fromnear zero to a large positive angle. During this transition the air flowaround the FEG is changing. The air flow through the rotors is straightdownward in hovering flight. This changes to a horizontal flow throughthe inclined rotor plane from underneath and continuing downwind of therotor with an added downward component of velocity in kite-like flight.During flight of prior art FEGs, when an angle of attack of the rotorsis at a relatively small angle θ, see FIG. 5, the downward component ofthe air flow emerging downwind of each forward rotor caused a reductionin thrust of an aft rotor mounted directly downwind of the forwardrotor. This is because the downward component of flow behind the forwardrotor changes the apparent wind direction for the aft rotor. Theapparent wind experienced by an aft rotor downwind of a forward rotorhas a downward component, which is equivalent to a relative reduction inpitch angle for that aft rotor. Reduction of pitch angle in the priorart FEGs thus reduced thrust that resulted in a rapid and uncontrolledincrease in vehicle pitch. However, unlike the prior art, because of thespacing of the front rotors relative to the rear rotors of the FEG ofthe present invention is such that no air passing through the frontrotors enters into the rear rotors, regardless of the angle of attack ofthe rotors, the rear rotors will always receive clean air and thuscontrol of the FEG in flight is enhanced.

The FEGs of this invention can have any number of sets of four rotors,simply by adding pairs of counter-rotating rotors to the left and rightof the core group of four rotors described above. The direction ofrotation of the additional sets must follow the rules for the originalset of four, and may be the same or opposite from the adjacent set ofrotors, see the arrangement of FIG. 12 which is another embodiment ofthe present invention. In the FEG 150 of FIG. 12, the fuselage 136 hasbeen extended and an additional pair of fore and aft counter rotatingrotors 137, 138 and 139, 140 have been mounted outwardly of the set offour inner rotors. The rotors 137 and 138 are mounted at the free endsof fuselage forward arms or booms 141 and 142, respectively, and therotors 139 and 140 are mounted on the free ends of fuselage aft arms orbooms 143 and 144.

The rotors of the interior set of four rotors shown in FIGS. 12, 13, 14,and 16 include two closely spaced forward rotors 122 and 123 and two aftrotors 128 and 129 that are spaced outwardly of the forward rotors so asto receive clean air as has been previously described. The interior fourbooms include two forward boom arms 124A and 124B and two aft boom arms127A and 127B. Further, as opposed to having the interior four boomsextending from a single central housing 26 as described with respect toFEG 20, two spaced housings 26A and 26B are shown from which the centralfour booms extend. Although the central four booms may be oriented asshown in FEG 20, they are shown in FIGS. 12, 13, 14, 15, and 16 with avaried orientation, however, the clean air spacing of the rotorsdiscussed herein must be maintained between the fore and aft rotors.Thus, the spacing of the rotors in the embodiment of FIGS. 12, 13, 14,and 15 is such that, in the direction of the wind shown by arrow “A”,none of the back drafts from the forward or fore rotors 137, 122, 123and 138 adversely effects clean air entering the aft rotors 139, 128,129 and 140.

The FEG 150 must have a method for one or more tethers to attach it tothe ground. Also, there must be structure to support the FEG whenlanding on the ground and allow it to take off again. The fuselage ofthe FEG 150 must meet these requirements. There are several arrangementsand structural configurations along with different materials andconstruction methods that can be used to construct the FEG 150 fuselage.

The fuselage of the FEG 150 includes housing structures 145, 26A and26B, which are similar to those shown at 26 of FEG 20, but have only twoboom arms extending therefrom, one forward and one aft. As shown, therotors mounted to the forward booms are more closely spaced than thecounter-rotating rotors mounted to the aft boom arms. The housings arepreferably fabricated from a combination of machined aluminum plates andformed sheets, but also could be fabricated from a multi-part ormonolithic composite material. The center section is used to contain theavionics and computer systems necessary for FEG control, the electronicsnecessary to communicate with the ground, the motor control electronics,and power conversion electronics. These will preferably be contained insealed enclosures to prevent moisture and particulate contamination fromdamaging the function of the electronics.

As opposed to the single point tethers associated with the FEG 20, withrespect to the larger FEG 150 of FIGS. 12, 13, 14, 15, and 16, andothers having more than the minimum four rotors, multiple tethers may beused to secure the FEGs to ground. These may be individual tethers eachconnected to the ground, or may be joined near the FEG with a bridlearrangement 146. As shown in FIG. 13, the bridle includes a primarytether 147 to ground and two lateral tethers 148 and 149 anchored to theouter central housings 145 of the outer rotors of FEG 50. The bridle maybe a balanced type as previously known or an actively controlled systemincluding mechanisms 160 for adjusting the length of the bridle elementsfrom the vehicle to the convergence points of the tether intersectionsshown in FIG. 13. As shown in FIG. 13, two additional tethers 151 and152 are mounted between the lateral tethers 148 and 149 and the centralhousings 145 of the two pair of inner rotors.

Multiple tether attachments can save structural weight, as bending inthe fuselage may be reduced or eliminated. For example, attaching themultiple tethers to the fuselage at or very near each rotor would reactthe wind forces on each rotor almost directly into the tether. Anotherapproach locates the multiple attach points between each set of rotors,reducing the requirement for the fuselage to react to bending loads tothe portion of the fuselage between those rotors. If the sets of rotorsconnected to each tether attach include one forward and one aftcounter-rotating pair of rotors, and the tether attach points are alonga transverse axis including the vehicle center of gravity and geometriccenter of rotor areas, then pitch maneuvers can be made withoutadjusting the length of the bridle elements, by adjusting rotor bladepitch only. This is advantageous as winching mechanisms used to changethe length of bridle elements react slowly compared to changing rotorblade pitch. Quick response in changing FEG pitch angle is desirable tominimize the effect of gusts, which rapidly increase thrust and tethertension. Additionally, winching mechanisms are costly, use power and addweight to the FEG. This multiple tether attachment scheme would requireadjustable length elements to achieve roll maneuvers. Roll anglevariations are not necessary for tether tension relief and can be mademore slowly, so winching control is acceptable.

A FEG 150 with eight or more rotors (four counter-rotating pairs) can beconfigured as shown in FIGS. 12, 13, 14, 15, and 16. Each pair of rotorsis made up of a forward rotor 137, and an aft rotor 139. The forwardrotor 137 is upwind of the aft rotor 139, and the aft rotor 139 isfarther from the centerline (shown in FIG. 14) of the FEG 150. Anynumber of pairs of rotors following this scheme may be added to thevehicle, as long as the same number are on each side of the FEG 150centerline 170, and the rotors on opposite sides of the centerline 170at the same relative placement rotate in opposite directions. Each rotorhas blades 160. Each rotor is mounted to a shaft (not shown) that isheld in bearings (not shown) in a rotor housing (137 a, 138 a, 139 a,140 a, for example), which also include an electric motor/generator (notshown). This motor (not shown) can be of any type, though permanentmagnet rotor multi-pole motors are preferred, and have any kind of driveto the rotor shaft including geared, belt driven or direct drive, whichis preferred.

The vehicle structure can be made from a main transverse boom orfuselage 136, shown as a large round tube, plus several diagonal tubularstructural members 141 connecting each pair of forward (137, 122, 123,138) and aft rotors (139, 128, 129, 140). The diagonal tubularstructural members or booms (141, 143, for example) have a centralhousing 145 that connects them to the main transverse boom or fuselage136. This attachment can be made to allow rotation relative to the axisA of the transverse boom or fuselage 136 through small angles α, up to10 degrees each direction. Rotation past 10 degrees each direction wouldbe prevented by a mechanical stop. This rotation may be allowed tofreely move, and the angle maintained by balancing thrust of the pair ofrotors attached to each diagonal structural member or boom (141, 143,for example), or preferentially, the angle of each diagonal structuralmember or boom (141, 143, for example) relative to the transverse boomor fuselage 136 is controlled by a motor and gear drive. This rotation,when made on the diagonal structural member or boom (141, 143, forexample) farthest from the centerline 170, in opposite directions willcreate an opposing horizontal component of the thrust from the pair ofrotors (137, 139) attached to that diagonal structural member or boom(141, 143) which will result in a large torque about the FEG 150vertical axis. This torque is useful for controlling yaw rotations ofthe vehicle. This rotation is shown in FIG. 16.

Tether attachment to a vehicle of this configuration may bealternatively done with multiple tethers to each rotor housing (notshown), or to at least 4 of the rotor housings in a symmetricarrangement (not shown) around the vehicle centerline 170, or to twopoints equally spaced (not shown) from the centerline 170 along the maintransverse boom or fuselage 136. Alternatively, a single, centrallymounted tether 147, as shown in FIG. 16, can be used also, and ispreferred.

Although the diagonal tubular structural members or booms in FIGS. 12,13, 14, 15, and 16 are shown to be generally the same length, it isenvisioned that forward and aft diagonal tubular structural members orbooms may be different lengths as shown in FIG. 6.

An alternative embodiment of an FEG 250 with eight or more rotors (fourcounter-rotating pairs) can be configured as shown in FIGS. 17, 18, and19. Each rotor having blades 260. Each pair of rotors is made up of aforward rotor (237, 222, 223, 238), and an aft rotor (239, 228, 229,240). The forward rotor (237, 222, 223, 238) is upwind of the aft rotor(239, 228, 229, 240), and the aft rotor (239, 228, 229, 240) is fartherfrom the centerline 270 of the FEG 250. Any number of pairs of rotorsfollowing this scheme may be added to the vehicle, as long as the samenumber are on each side of the FEG centerline 270, and the rotors onopposite sides of the centerline 270 at the same relative placementrotate in opposite directions. Each rotor is mounted to a shaft that isheld in bearings in a rotor housing (237 a, 222 a, 223 a, 238 a, forexample), which also includes an electric motor/generator. This motorcan be of any type, though permanent magnet rotor multi-pole motors arepreferred, and have any kind of drive to the rotor shaft includinggeared, belt driven or direct drive, which is preferred.

A simple structure connecting these housings (237 a, 222 a, 223 a, 238a, for example) is shown in FIGS. 17, 18, and 19, made of tubularstructural member transverse booms (236 a, 236 b) connecting each motortransversely on the front 236 a, and aft 236 b sides of the FEG 250, andalso booms (241, 224A, 22413, 242) connecting each pair of forward andaft rotors. Other arrangements are possible, including adding additionaldiagonal struts from an outer forward rotor housing 222 a across towardsthe longitudinal centerline 270 of the FEG 250 to an aft rotor housing228 a closer to the centerline 270.

Tether attachment to a vehicle of this configuration may be done withmultiple tethers to each rotor housing (not shown), or to at least 4 ofthe rotor housings in a symmetric arrangement (not, shown) around theFEG centerline 270, or to two points near the center of the diagonalstructural members 224A and its opposite side 22413. Preferred tetherconfiguration is a single, centrally mounted tether 247. A singlemounted tether 247 can be used if additional central structure andcentral tether attach node 280 are added to the central portion of theFEG to mount the single tether. The central structure may be configureddifferently, and may consist of booms diagonally connecting the fourrotor housings (222 a, 223 a, 228 a, 229 a) nearest the center of theFEG 250, and the central tether attach node 280, or a single lateralboom 290 along the FEG centerline 270 which is preferred.

The foregoing description of the preferred embodiment of the inventionhas been presented to illustrate the principles of the invention and notto limit the invention to the particular embodiment illustrated. It isintended that the scope of the invention be defined by all of theembodiments encompassed within the following claims and theirequivalents.

We claim:
 1. A flying electric generator comprising a transverse boom,at least a first pair of boom arms extending forward from and laterallyoutwardly of the transverse boom and have outer ends, at least a firstpair of counter rotating first rotors being mounted along the outer endsof the at least first pair of boom arms, at least a second pair of boomarms extending aft and laterally outwardly from the transverse boom andhaving outer ends, at least a first pair of second counter rotatingrotors mounted along the outer ends of the at least second pair of boomarms, wherein each of the rotors is mounted to the transverse boom suchthat when the at least first pair of first rotors are leading into thewind, each of the at least first pair of first rotors and the at leastfirst pair of second rotors is positioned so as to receive a direct pathto an undisturbed flow of wind regardless of angle of attack or pitchangle of the flying electric generator, and wherein each pair of boomarms is attached to the transverse boom to allow rotation of each pairof boom arms relative to the axis of the transverse boom.
 2. The flyingelectric generator of claim 1 wherein each pair of boom arms rotate 10degrees in each direction about a transverse axis of the transverseboom.
 3. The flying electric generator of claim 1 wherein each pair ofboom arms rotate less than 10 degrees in each direction about atransverse axis concentric with the transverse boom.
 4. A flyingelectric generator comprising a front transverse boom and an afttransverse boom, at least a first pair of counter rotating first rotorsmounted along the front transverse boom and the aft transverse boom, atleast a second pair of counter rotating first rotors mounted along thefront transverse boom and the aft transverse boom, the front transverseboom and aft transverse boom connected at the first pair of counterrotating first rotors by a first pair of boom arms and at the secondpair of counter rotating first rotors by a second pair of boom arms, thefirst pair of boom arms are located on opposite sides of a centerline ofthe flying electric generator and the second pair of boom arms arelocated on opposite sides of a centerline of the flying electricgenerator, wherein the second pair of boom arms are located closer tothe centerline of the flying electric generator than the first pair ofboom arms, and wherein each of the rotors is mounted to the fronttransverse boom and aft transverse boom such that when the at leastfirst pair of first rotors are leading into the wind, each of the atleast first pair of first rotors and the at least first pair of secondrotors is positioned so as to receive a direct path to an undisturbedflow of wind regardless of angle of attack or pitch angle of the flyingelectric generator.
 5. The flying electric generator of claim 4 whereinthe second pair of boom arms are oriented diagonally such that therotors mounted on the front transverse boom are more closely spaced tothe centerline of the flying electric generator than the rotors mountedto the aft transverse boom.
 6. The flying electric generator of claim 4further comprising a single centrally mounted boom arm with a centraltether attach node, wherein a single tether is attached to the centraltether attach node.
 7. The flying electric generator of claim 4 furthercomprising a tether attach node on each boom arm, wherein a pair oftethers are mounted to the tether attach nodes of one pair of boom arms.8. The flying electric generator of claim 4 further comprising a tetherattach node on each boom arm, wherein a set of tethers is attached tothe tether attach node of each boom arm.